Top all-time · #38
John D. Cook
Personal blog · johndcook.com/blogmathprogramming
John D. Cook's personal blog at johndcook.com covers math and programming. Since 2009, 654 different Hacker News readers have linked it 1,940 times, most often “Gell-Mann amnesia and its opposite”. It is still writing: the last post was on 2026-11-01, and you can follow it by feed.
Rarely recommended · 4 of 40 sampled comments recommend it?
Why HN links it
HN readers cite it as a reference for short explanations of math and computing: queueing theory, floating point, matrix inversion, probability distributions. Some list it among favourite blogs.
- Recommended for · 4 comments
- One commenter calls a Little's Law post nice; one finds a distribution chart handy; two list it as a favorite.
Summarised by Claude from a sample of 40 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
Companies come to us for help data analysis and data privacy. Clients have included Amazon, Google, Microsoft, law firms, start-ups, and smaller businesses.
Most-linked posts?
- Gell-Mann amnesia and its opposite13 people · 13 mentions · first linked 2021-05-12
- How to fit an elephant (2011)11 people · 12 mentions · first linked 2017-06-09
- What happens when you add a new teller? (2008)10 people · 12 mentions · first linked 2019-02-03
- You Wanted a Banana but Got a Gorilla Holding the Banana and the Entire Jungle10 people · 10 mentions · first linked 2018-06-20
- Anatomy of a Posit Number9 people · 9 mentions · first linked 2018-04-12
- /blog/7 people · 7 mentions · first linked 2017-07-25
- Selection bias and bombers (2008)6 people · 6 mentions · first linked 2010-10-22
- Don’t invert that matrix (2010)6 people · 6 mentions · first linked 2010-01-19
- OO vs. FP programming6 people · 6 mentions · first linked 2010-11-04
- Don't invert that matrix (2010)6 people · 6 mentions · first linked 2017-02-25
What Hacker News says?
Posit numbers (a better floating point representation): https://www.johndcook.com/blog/2018/04/11/anatomy-of-a-posit... https://www.johngustafson.net/pdfs/BeatingFloatingPoint.pdf
Comment linking /blog/2018/04/11/anatomy-of-a-posit-number/
on “Ask HN: What are some cool but obscure data structures you know about?”Submitted Organizing complexity is the most important skill in software development as a story · 742 points
HN discussionPerhaps the people who care too much aren't that smart in this case. See the Napoleon anecdote: http://www.johndcook.com/blog/2010/12/27/dumb-and-gets-thing...
Comment linking /blog/2010/12/27/dumb-and-gets-things-done/
on “I quit the tech industry”Submitted Software reuse is more like an organ transplant than snapping Lego blocks (2011) as a story · 667 points
HN discussionIf you didn't know, that 80% number is probably the result of Little's Law. That's the result where if your demand is generated by a Poisson process, and your service has a queue, 80% utilization of the service is where the probability of an infinite queue starts to get really high. People Here's a nice blog post about the subject: https://www.johndcook.com/blog/2009/01/30/server-utilization...
Comment linking /blog/2009/01/30/server-utilization-joel-on-queuing/
on “Netflix to cut streaming quality in Europe for 30 days”Submitted 987654321 / 123456789 as a story · 637 points
HN discussionHELLO.C in question: https://www.johndcook.com/blog/2014/11/12/hello-world-is-the... I was unfamiliar.
Comment linking /blog/2014/11/12/hello-world-is-the-hard-part/
on “VS Code uses 13% CPU when idle due to blinking cursor rendering”Submitted Estimating the chances of something that hasn’t happened yet as a story · 575 points
HN discussionhttps://www.johndcook.com/blog/2023/08/12/fibonacci-lattice/ If you want a spiral that covers the sphere with evenly spaced samples, consider this approach.
Comment linking /blog/2023/08/12/fibonacci-lattice/
on “Show HN: I was curious about spherical helix, ended up making this visualization”Submitted Doing a database join with CSV files as a story · 357 points
HN discussionCover topics around software development, math, programming languages, and academia: http://stuffwithstuff.com/ https://ericlippert.com/ http://thume.ca/archive.html https://medium.com/@mdwdotla https://faculty.washington.edu/ajko/posts https://computinged.wordpress.com/ https://blog.acolyer.org/ https://blog.sigplan.org/blog/ https://blog.paranoidcoding.com/ https://blog.regehr.org/ https://eli.thegreenplace.net/ h…
Comment linking /blog/
on “Ask HN: Favorite Blogs by Individuals?”Submitted Four Hours of Concentration as a story · 334 points
HN discussionA couple of my favorite blogs - http://antirez.com/ - https://martin.kleppmann.com/archive.html - https://devblogs.microsoft.com/oldnewthing - https://ma.tt/ - https://www.allthingsdistributed.com/ - https://jvns.ca/ - https://www.johndcook.com/blog - http://feross.org/ - https://ridiculousfish.com/blog/ - https://blog.andrewcantino.com/ - https://nickcraver.com/blog/ - https://blog.acolyer.org - https://blog.coding…
Comment linking /blog
on “Ask HN: Favorite Blogs by Individuals?”Submitted Queueing theory: The science of waiting in line as a story · 299 points
HN discussionYou're not alone: https://www.johndcook.com/blog/2013/02/04/four-hours-of-conc...
Comment linking /blog/2013/02/04/four-hours-of-concentration/
on “Your own company? You can do it (2011)”Submitted Pretending OOP Never Happened as a story · 290 points
HN discussionOne quick comment: in general it is a bad idea to compute the inverse of a matrix (to solve a linear system). It's much better to compute the QR factorization or SVD instead (or simply call least square solver). See for example: https://www.johndcook.com/blog/2010/01/19/dont-invert-that-m...
Comment linking /blog/2010/01/19/dont-invert-that-matrix/
on “Machine Learning from scratch: Bare bones implementations in Python”Submitted Why programmers are not paid in proportion to their productivity as a story · 285 points
HN discussionThis is like having a weighted coin that comes up heads with probability 2⋅10⁻⁶, flipping it 311 million times, and seeing 0 heads. That's astronomically unlikely. To see this, observe that the number of heads follows a binomial distribution with n = 311 million and p = 2⋅10⁻⁶. This can be well approximated¹ by a normal distribution with mean μ = np = 622 and standard deviation σ = Sqrt[ np (1 - p )] = 25. 99.7% of…
Comment linking /blog/table-of-normal-tail-probabilities/
on “No person who was born blind has ever been diagnosed with schizophrenia”Submitted Golden powers are nearly integers as a story · 277 points
HN discussionOr, as Thomas Jefferson did, you overwhelm them with excessive preparation, so that they are reduced to making minor suggestions and your vision goes through. http://www.johndcook.com/blog/2011/03/03/thomas-jefferson-me...
Comment linking /blog/2011/03/03/thomas-jefferson-meetings/
on ““Just remove the duck” (2013)”Submitted Organizational Skills Beat Algorithmic Wizardry (2015) as a story · 268 points
HN discussionThis doesn't contain his most famous line on the topic: You wanted a banana but what you got was a gorilla holding the banana and the entire jungle. https://www.johndcook.com/blog/2011/07/19/you-wanted-banana/
Comment linking /blog/2011/07/19/you-wanted-banana/
on “Why OO Sucks by Joe Armstrong (2000)”Submitted Why does FM sound better than AM? as a story · 261 points
HN discussion...followup after looking through comments on OP, indeed someone else already had the idea to tie in OEIS sequences in the comment at https://www.johndcook.com/blog/2025/10/26/987654321/#comment... but i still wonder if there is something like OEIS for observations / analysis like this
Comment linking /blog/2025/10/26/987654321/
on “987654321 / 123456789”Submitted Why isn't everything normally distributed? as a story · 250 points
HN discussion> Lisp had 60 years to prove its human scaling capabilities. So far it hasn't convinced. It can take more than you might expect to "convince". > In 1601, an English sea captain did a controlled experiment to test whether lemon juice could prevent scurvy. He had four ships, three control and one experimental. The experimental group got three teaspoons of lemon juice a day while the control group received none. No one…
Comment linking /blog/2008/03/25/innovation-ii/
on “How Lisp Became God's Own Programming Language”Submitted Test for Divisibility by 13 as a story · 239 points
HN discussionhttps://www.johndcook.com/blog/2008/01/21/selection-bias-and...
Comment linking /blog/2008/01/21/selection-bias-and-bombers/
on “Things I’ve Learned from Reading IndieHackers”Submitted Where has all the productivity gone? as a story · 236 points
HN discussion
